Spraying apparatus

ABSTRACT

An apparatus for electrostatically spraying powdery material. A conveyor extends into a vessel which contains a supply of the material to be sprayed, this conveyor moving the material from the vessel to a point near a spraying zone. Means are provided for moving the material from this point into the spraying zone.

United States Patent Otto Renner Neu-laenburg, Germany May 22, 1969 Nov.16, 1971 Llcentia Patent-Ver waltungs-GJmbJl Frankfurt am Main, GermanyInventor Appl. No. Filed Patented Assignee Priorities May 22, 1968,Germany, No. P 17 52 410.6

SPRAYING APPARATUS 12 Claims, 6 Drawing Figs.

1 1 8/308 Int. Cl. H B05b 5/02 Field Search 118/308,

[ 56] References Cited UNITED STATES PATENTS 1,581,322 4/1926 Reed118/325 X 2,174,328 9/1939 Meston et al. 1 18/629 2,254,016 8/1941Melton et a1... 118/627 3,439,649 4/1969 Probst et al 1 18/312 X FOREIGNPATENTS 251,626 5/1964 Australia 1 18/308 Primary Examiner-John P.McIntosh Attorney- Spencer & Kaye ABSTRACT: An apparatus forelectrostatically spraying powdery material. A conveyor extends into avessel which contains a supply of the material to be sprayed, thisconveyor moving the material from the vessel to a point near a sprayingzone. Means are provided for moving the material from this point intothe spraying zone.

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FIG. 5

SPRAYING APPARATUS BACKGROUND OF THE INVENTION The present inventionrelates to an apparatus for electrostatically spraying a material whichis in powder form, which apparatus includes a conveyor that extends intothe vessel.

One way of coating work pieces is by means of the so-calledwhirl-sintering process, in which powdery material located in a vesselthat is open at the top is maintained in a suspended state by means of aweak current of air which is introduced into the vessel through anair-permeable bottom. The work piece to be coated is preheated to apredetermined temperature and is then dipped into the thus-loosedcoating material. In this way, a coating of predetermined thickness isformed on the surface of the workpiece, due to the temperature of thelatter. Next, the coating is firmly bonded to the surface of the workpiece, this being done in a suitable kiln. The thus-obtained coatingsare normally sufficiently well attached to the work piece. Onesignificant drawback of this process, however, is that only certaintypes of workpieces will lend themselves to being subjected to thepreheating step before being dipped into the suspended material,inasmuch as the temperature to which the workpiece must be heated inorder to cause the particles to adhere properly is quite high.

Various ways have been proposed in which to coat workpieces with powderymaterial, some of these ways involving electrostatic processes, namely,processes in which the material is brought into the spraying zone byapplying a high voltage to one of the spraying parts. The difficultyhere is that special measures are required in order to deposit thematerial uniformly along the entire length of the work piece.

SUMMARY OF- THE INVENTION It is therefore, the primary object of thepresent invention to provide a wayv of electrostatically spraying aworkpiece which overcomes the above drawback, namely, to provide a wayin which powdery material can beapplied uniformly by means of anelectrostatic apparatus. In accordance with the present invention, thisis accomplished by providing conveyormeans which bring the powderymaterial to a point near the spraying zone and by providing means whichmove the material from this point into the spraying zone. This is donebecause the electrostatic force between the workpiece to be coated andveyor, the same being constituted by an endless belt 4 which passes overat least two, rollers and which is driven so as to move in the directionof the arrow 5. The spray wires 6, which are located in the sprayingzone and which are connected to a source of high voltage (not shown),are arranged in front of the conveyor belt 4, i.e., or that side thereofwhich is directed toward the spraying zone. A tapping mechanism 7 islocated behind conveyor belt 4, i.e., at the side thereof which isdirected away from the spraying zone, and is at the same level as thespray wires 6. The workpieces 8 which are to be coated with the material2 are located at a suitable distance away from the conveyor belt 4,these work pieces being carried by a conveyor 9 which serves both toground the work pieces and to carry them through the spraying zone inthe direction of the arrow 10.

The conveyor belt 4 which carries the material to be sprayed to a pointnear the spraying zone may be made of insulating material. In order tomake certain that the conveyor belt will-be able to convey sufficientmaterial into the spraying zone, the belt is roughened or is deformed soas to be other than absolutely flat. Alternatively, the conveyor beltmay be made of a strandlike material which is intertwined, interwoven ornetted into a conveyor belt. Yet another possibility is to provide aconveyor belt one of whose sides has a hidelike or brushlike surface.The tapping mechanism 7 is suitably ar ranged so as periodically to tapthe conveyor belt. This can be done, for example, by providing a tappingmechanism in the fonn of a vibrator. Alternatively, means can beprovided which cause a gaseous stream to blow the material from theconveyor belt 4 and into the spraying zone; this, it will be understood,presupposes that the conveyor belt be air-permeable. In practice, thegaseous medium used to move the material from the conveyor belt to theworkpieces to be coated will be an inert gas, thereby to prevent anypossible danger or damage due to combustion. Yet another way in whichthe the spraying part forming part of the electrostatic equipment isnormally not sufficient to effect this movement in such a way as toproduce uniform coating.

BRIEF DESCRIPTION OF TI-IE DRAWINGS FIG. 1 is a schematic view of anelectrostatic spraying apparatus according to the present invention.

FIG. 2 is a plan view of a multiple-unit electrostatic sprayingapparatus according to the present invention.

FIG. 3 is a front view of the electrostatic spraying apparatus shown inFIG. 1.

FIG. 3a is a front view of a portion ofthe apparatus of FIG. 3 showing apreferred modification thereof.

FIG. 4 is a fragmentary view, on an enlarged scale, of a detail of thestructure shown in FIG. 3.

FIG. 5 is a plan view of a multiple-unit electrostatic sprayingapparatus according to the invention for simultaneously spraying aplurality of surfaces of a three-dimensional workpiece.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawingsand first to FIG. 1 thereof, the same shows an electrostatic sprayingapparatus according to the present invention, the same incorporating anopen vessel 1 containing a supply of the material 2 which is in powderform and which is to be applied by electrostatic spraying. This material2 is loosened, in a manner known per se, in whirl sintering by means ofan airstream, indicated by the arrows 3, which is passed upwardlythrough the air-permeable bottom of the vessel 1. The material is takenout of the vessel 1 by a conmaterial can be moved from the conveyor beltto the work pieces is by providing an ultrasonic wave source.

If the means for removing the material from the conveyor belt are in theform of the above-described tapping mechanism 7, the tension of theconveyor belt 4 may suffice to move the material out of the belt andinto the spraying zone. Alternatively, the spray wires 6 may be used asabutments against which the tapping means strike. In order to preventthe wires from being subjected to undue mechanical wear, there may beprovided a suitable powder-permeable abutment 11 which allows thepowdery material 2 to pass through.

Normally, a single spray applicator unit of the type described abovewill suffice to coat flat workpieces to the desired thickness. Ifthicker coatings are desired, however, the apparatus may include aplurality of individual units each as described above, the same beingrepresented schematically, in FIG. 2, by the respective conveyor belts4a, 4b, 40. As will be seen from FIG. 2, the several units are arrangedin a line extending generally in the same direction as that in which theworkpieces 8 are conveyed. In order that the material 2 will bedeposited uniformly, adjacent conveyor belts are run in oppositedirections. Thus, the reaches of the two end conveyor belts 4a and 4c,for example, which face the spraying zone will, in the arrangementdepicted in FIG. 2, run from top to bottom (as seen in FIG. 1) and thecorresponding reach of the conveyor belt 4b-which is between theconveyor belts 4a and 4' wm run from bottom to top.

If the workpieces to be sprayed are relatively large in all threedimensions, i.e., if more than one surface of a workpiece is to besprayed, the individual units may be so arranged that the conveyor beltsof all units surround the workpiece on all sides. Such an arrangement isshown, for example, in FIG. 5 for a workpiece of rectangular crosssection whereby four spraying units are utilized. I

FIG. 3 again shows the vessel 1 containing the material 2. Air isintroduced into the bottom of the vessel 1 by way of the air inletconduit 3. The conveyor belt 4' is here shown as being constituted by aloose web, the belt being run over rollers l2 and 13, the latter beingmounted for rotation within vessel 1 and below the level of the material2. The other roller 12, which is mounted above the vessel, is driven bya motor 14. The conveyor belt 4' is prevented from running off therollers l2, 13, by means of a belt which has a V-shaped cross sectionand which itself runs in V-shaped grooves that are provided in the tworollers. The conveyor belt 4' is suitably secured to the surface of theV-shaped belt 15, as, for example, by being glued thereto. Byappropriately inclining the axis of roller 12 at a small angle arelative to the axis of the roller 13, as shown in FIG. 3a, the conveyorbelt 4' can be given a tendency to run onto the belt 15 rather than awayfrom it.

FIG. 4 is similar to the upper part of FIG. 3 but shows the roller 12 asbeing provided with a helical ridge 19, the purpose of which is toprevent the belt 4 from running off the roller. If desired, both rollers12 and 13 may be provided with such helical ridges.

By virtue of the above, it will not be necessary periodically to stopthe operation of the apparatus in order to readjust the position of theconveyor belt on the rollers. This is of particular significance wherethe conveyor belt is constituted by loose webbing or the like which, butfor the above-described measures, would have a marked tendency to wanderoff the rollers.

It will be understood that the above description of the presentinvention is susceptible to various modifications, changes andadaptations.

I claim:

1. In an apparatus for electrostatically spraying powdery material ontoa surface, the improvement comprising, in combination:

a. a vessel for containing a supply of the powdery material to besprayed;

b. means for maintaining the powdery material in said vessel in afluidized state;

c. conveyor means including a conveyor belt and roller means for guidingsaid conveyor belt, said conveyor means extending down into said vesselfor removing said powdery material from said vessel and moving same to apoint adjacent an electrostatic spraying zone; and

d. means for causing said powdery material to be moved from said pointinto said spraying zone.

2. Apparatus as defined in claim 1, wherein the axes of said rollers areat an angle to each other.

3. Apparatus as defined in claim 1, wherein said means d comprise atapping mechanism arranged on that side of said conveyor belt which isdirected away from said spraying zone and an abutment which is on theopposite side of said conveyor belt and hence on that side which isdirected toward said spraying zone, said abutment means beingpowder-permeable to allow the passage therethrough of said material.

4. Apparatus as defined in claim 3, wherein said abutment means comprisewires which are electrically connected to a source of high voltage andwhich themselves thus form part of a means for applying an electrostaticcharge to said material to be sprayed.

5. Apparatus as defined in claim 1, wherein said vessel is open at itsupper end and wherein said conveyor belt is guided by said rollers sothat it moves in a substantially vertical direction.

6. Apparatus for electrostatically spraying powdery material,comprising, in combination:

a. a vessel for containing a supply of the material to be sprayed;

b. conveyor means extending into said vessel for moving the materialfrom said vessel to a point near a spraying zone, said conveyor meansincluding a conveyor belt and roller means for guiding said conveyorbelt, said roller means include at least two rollers each having aV-shaped groove and said conveyor means further comprise a V- shapedbelt connecting said rollers and running in said grooves thereof, atleast one of said rollers having a helical ridge; and

c. means for moving the material from said point into said sprayingzone.

7. Apparatus as defined in claim 5, wherein one edge of said conveyorbelt is connected to said V-shaped belt.

8. In an apparatus for electrostatically spraying powdery material ontoa surface, the improvement comprising, in combination:

a. a vessel for containing a supply of the powdery material to besprayed;

b. means for maintaining said powdery material in said vessel in afluidized state;

c. conveyor means including an air-permeable conveyor belt and rollermeans for guiding said conveyor belt, said conveyor means extending downinto said vessel for removing said powdery material from said vessel andmoving same to a point adjacent an electrostatic spraying zone; and

d. means for blowing a stream of gaseous medium through said conveyorbelt from that side thereof which is directed away from said sprayingzone to cause said powdery material to be conveyed into said sprayingzone.

9. Apparatus as defined in claim 8, wherein said conveyor belt has aroughened or deformed surface.

10. Apparatus as defined in claim 8, wherein said conveyor belt is madeof a strandlike material which is intertwined, interwoven or netted.

11. Apparatus as defined in claim 8, wherein said conveyor belt has ahidelike or brushlike surface.

12. An arrangement for electrostatically spraying powdery material ontoall sides of a workpiece, comprising a plurality of apparatuses each asdefined in claim 8, the said apparatuses being arranged such that theconveyor belts of all of said apparatuses surround the workpiece.

1. In an apparatus for electrostatically spraying powdery material ontoa surface, the improvement comprising, in combination: a. a vessel forcontaining a supply of the powdery material to be sprayed; b. means formaintaining the powdery material in said vessel in a fluidized state; c.conveyor means including a conveyor belt and roller means for guidingsaid conveyor belt, said conveyor means extending down into said vesselfor removing said powdery material from said vessel and moving same to apoint adjacent an electrostatic spraying zone; and d. means for causingsaid powdery material to be moved from said point into said sprayingzone.
 2. Apparatus as defined in claim 1, wherein the axes of saidrollers are at an angle to each other.
 3. Apparatus as defined in claim1, wherein said means d comprise a tapping mechanism arranged on thatside of said conveyor belt which is directed away from said sprayingzone and an abutment which is on the opposite side of said conveyor beltand hence on that side which is directed toward said spraying zone, saidabutment means being powder-permeable to allow the passage therethroughof said material.
 4. Apparatus as defined in claim 3, wherein saidabutment means comprise wiRes which are electrically connected to asource of high voltage and which themselves thus form part of a meansfor applying an electrostatic charge to said material to be sprayed. 5.Apparatus as defined in claim 1, wherein said vessel is open at itsupper end and wherein said conveyor belt is guided by said rollers sothat it moves in a substantially vertical direction.
 6. Apparatus forelectrostatically spraying powdery material, comprising, in combination:a. a vessel for containing a supply of the material to be sprayed; b.conveyor means extending into said vessel for moving the material fromsaid vessel to a point near a spraying zone, said conveyor meansincluding a conveyor belt and roller means for guiding said conveyorbelt, said roller means include at least two rollers each having aV-shaped groove and said conveyor means further comprise a V-shaped beltconnecting said rollers and running in said grooves thereof, at leastone of said rollers having a helical ridge; and c. means for moving thematerial from said point into said spraying zone.
 7. Apparatus asdefined in claim 5, wherein one edge of said conveyor belt is connectedto said V-shaped belt.
 8. In an apparatus for electrostatically sprayingpowdery material onto a surface, the improvement comprising, incombination: a. a vessel for containing a supply of the powdery materialto be sprayed; b. means for maintaining said powdery material in saidvessel in a fluidized state; c. conveyor means including anair-permeable conveyor belt and roller means for guiding said conveyorbelt, said conveyor means extending down into said vessel for removingsaid powdery material from said vessel and moving same to a pointadjacent an electrostatic spraying zone; and d. means for blowing astream of gaseous medium through said conveyor belt from that sidethereof which is directed away from said spraying zone to cause saidpowdery material to be conveyed into said spraying zone.
 9. Apparatus asdefined in claim 8, wherein said conveyor belt has a roughened ordeformed surface.
 10. Apparatus as defined in claim 8, wherein saidconveyor belt is made of a strandlike material which is intertwined,interwoven or netted.
 11. Apparatus as defined in claim 8, wherein saidconveyor belt has a hidelike or brushlike surface.
 12. An arrangementfor electrostatically spraying powdery material onto all sides of aworkpiece, comprising a plurality of apparatuses each as defined inclaim 8, the said apparatuses being arranged such that the conveyorbelts of all of said apparatuses surround the workpiece.